Esters of trichloroacetic acid



Patented Apr. 7, 1953 ESTERS OF TRICHLOROACETIC ACID Joseph A. Sonia and Eric H. Scremin, Niagara Falls, N. .Y., assignors to Hooker ElectrochemicalCompany, Niagara Falls, N. Y., a corporation of New .York

No Drawing. Application May 5, 1951, Serial No. 224,826

This invention relates to new esters-of trichloroacetic acid, prepared by reacting trichloro acetic acid with dihydroxy aliphatic alcohols, and more particularly to bis(trichloroacetates) of dihydroxy aliphatic alcohols and dihydroxy ethers :having the following general formula:

wherein R represents an alkylene .or oxyalkylene group having two or more, carbon atoms.

."Ihis application is a continuation-in-part'of our co-pending application -S. N. 177,956 filed August 5,1950.

The novel esters of trichloracetic acid of this invention can "be obtained by reacting trichloro acetic acid with :an aliphatic glycol or glycol ether, under conditions-which :effect esterification. Among the dihydroxy aliphatic alcohols whichmay'be used are ethylene glycol, propylene glycol, ibutane-diol, pentane-diol, hexane-diol, etc;; among the dihydroXy ethers or glycolethers which may be used are diethylene glycol, triethylene glycol, dipropylene glycol, ,etc. The new compounds are characterized as being sub; stantially clear water whit oils or white ,crys: talline solids, insoluble in water, non-flammable; of mild odor and 'nonwirritating to the skin of man.

The new esters may be prepared by'condu'cting the reaction of the acid component .and'the dihydroxy aliphatic alcohol, in the presence of a compound which forms an azeotrope with water, preferably with heating whereby high yields of the desired product may be realized;

however, the presence of an iazeotrope 513.1101? es: sential in this reaction in order to obtain the desired product. Among the compounds which form azeotropes with water which we have found useful in giving good yields of product are toluene, benzena'xylene, pentane,'hexane and-hydrocarbon materials in general which are immiscible with water.

If desired, alcatalyst such as an inorganicaoim e. .g. sulphuric acid; acid salt, e. g. sodium acid.

sulphate; .benzenelsulph'onic acid; p-toluene sulphon'ic acid, etc, may be employed in the prep:

aration of our novel compounds, to promote rapid reaction atrelatively low temperatures, but. the reaction proceeds smoothly and rapidly in the :absence of such catalysts under the conditions described above.

"7 Claims. (Cl. 260-487) A preferred. procedure for preparing the .com-i. pounds of this invention involves: introducin about two moles of .acid component, one mole of dihydroxy aliphatic alcohol and sufficient entrainer (such as toluene, which forms an azeotrope with water, .to effect the separationof the water of reaction from the mixture) into an esterification still (which includes a refluxcolumn, means for returning the organics to the reaction vessel and means for separating the water of reaction from the refluxed organics) and refluxing the reaction mixture until substantially no more water of reaction is separated. Upon completion .of the reaction, the toluene is distilled from thereaction mixture. The desired product may be recovered insubstantially pure form by a simple distillation from the ester still and/or by a washing with water or weaksodium bicarbonate solution in order to remove any une reacted alcohol and/or acid, depending upon the nature of the crude reaction product.

In order to prepare substantially pure esters of this invention, it is not essential that pure trichloroacetic acid be used as the acidcomp'ee nent. We have found is convenient and 'economical .to employ .the trichloroacetic acid de rivative containing .trichloracetic acid, trichloroacetic .anhydride and .trichloroacetyl chloride, produced .bythe method ofour co-pending appli cation, referred to above, as a convenient source of raw material for the acid component. The aliphaticglycols and glycolethers such as ethylene glycol, diethylene glycol and 1,2-propylene glycol, butane-diol-LZ etc; which are readily available in commercial quantities are preferably used as the source ,forthe ,dihydroxy .alcoholcornponent in this reaction because of the economy involved.

The novel esters of this invention may also be prepared by other known procedures for preparing esters of the type .expressedlby the general formula given above, including the simple re: action, with heating, if necessary, of the carboxyl group of the acid component with the hydroxy groups of the alcoholic component whereby water is eliminated, or, by the reaction of the anhydride of the acid component with the hydroxy groups of the alcohol, or, by the re-. action of an acid chloride of .theacid component, e. g. trichloroacetyl chloride, with the dihydroxy aliphatic alcohol whereby hydrogen chloride is liberated.

The compounds of the present invention .can be usefully employed as plasticizers for resins, particularly cellulose resins, e. g. cellulose acetate; as solvents'or softening agents; as 'herbi- Example I .-Ethylene glycol bis(trichloroacetate) Seventeen moles (2781.5 grams) of trichloroacetic acid together with 750 grams of toluene and 7.5 moles (465 grams) of ethylene glycol were charged into a five liter glass flask arranged as an esterification still. The esterification still arrangement includes means for heating the reaction vessel, a thermometer, a reflux condenser having cooling means, means for separating the water of reaction from the refluxing organics, and means for returning the organics to the re: action vessel. The charge was heated to a temperature between about 100 and 150 degrees centigrade and refluxed until water of reaction was no longer separated, which was after 15.4 moles (278.7 grams) of water had been removed. The reaction mixture remaining in the esterification still was washed with four separate portions of water. The washed material was then distilled under vacuum; a first cut totaling 750 cc. was separated at a vapor temperature or boiling range of about 41 to 44 degrees centigrade at an :absolute pressure between 95 and 72 mm. of mercury; a second cut totaling 80 cc. and containing about 0.22 moles (80.4 grams) of ethylene glycol bis- (trichloroacetate) was separated at a boiling range of between 89 and 140 degrees centigrade at an absolute pressure between 72 and 2 mm. of mercury, and a third cut totaling 246'? grams was recovered, boiling at 146 degrees centigrade at an absolute pressure of 2 mm. of mercury, and represented 6.93 moles of ethylene glycol bis(trichloroacetate) which was equivalent to a 92.5 per cent yield of theory of ethylene glycol bis(trichloroacetate) based on the glycol charged. The ethylene glycol bis(trichloroacetate) recovered as the third cut was analyzed and characterized as having the following properties:

Per cent chlorine found 59.95 Per cent chlorine theory 60.3 Melting point C 39.5 Specific gravity at 51 C 1.592 Boiling point at 2 mm. Hg "C 146 Appearance, Tan colored crystalline solid.

A portion of the tan colored product recovered above, was further purified by washing a molten sample of it with a dilute aqueous solution of sodium bicarbonate and redistilling under vacuum. The melting point of the so purified product was redetermined and found to be 40.3 degrees centigrade.

Example II Example III .Dz'ethylene glycol bis- (trichloroacetate) of toluene were charged into an esterification still. The charge was refluxed until the formation of water ceased, which was after 17.7 moles (319 grams) of water had been separated. The reaction mixture remaining in the esterification still was washed with water and then distilled under vacuum. Six and eighty nine-hundredths moles (2801 grams) of diethylene glycol bis(trichloroacetate) was recovered having the following analysis and characteristics:

Per cent chlorine found 53.3 Per cent chlorine theory 53.7 Refractive index at 20 C 1.4908

Boiling range at between 4 and 7 mm. Hg C 184-199 Specific gravity at 24 C 1.5448 Appearance, Water white oily liquid.

Emample I V.-Propylene glycol-1,2-bis- (trichloroacetate) In a manner after the foregoing examples, 8.03 moles (1213 grams) of trichloroacetic acid together with 4.18 moles (318 grams) of propylene glycol-1,2 and 300 grams of toluene were charged into an esterification still and the charge refluxed until the formation of water ceased, which was after 7.77 moles grams) of water had been separated. The reaction mixture remaining in the esterification still was then distilled under vacuum. Three and ninety five-hundredths moles (1452 grams) of-propylene glycol-1,2-bis- (trichloroacetate) was recovered having the following analysis and characteristics:

Per cent chlorine found 55.5 Per cent chlorine theory 58.1 Refractive index at 20 C 1.4855 Boiling point at 1 mm. Hg C 147 Specific gravity at 25 C 1.5485

Appearance, Water white oily liquid.

Example V.Butane-diol-1,3-b2's- (trichloroacetate) Per cent chlorine found 54.5 Per cent chlorine theory 55.9 Refractive index at 20 C 1.4830

Boiling range at 1 mm. Hg C 142-147 Specific gravity at 25 C 1.4986 Appearance, Water white oily liquid.

Example VI.-Pentane-diol-2,4-bis- (trichloroacetate) In a manner after the foregoing examples, 8.53 moles (1393 grams) of trichloroacetic acid together with 4.18 moles (435 grams) of pentanediol-2,4 and 150 grams of toluene were charged into an esterification still. The charge was refluxed until no more water was separated which was after 7.9 moles (142 grams) of Water had been separated. The remaining reaction mixture was vacuum distilled. Four-and-five-hundredths aaaeanec moles (1600 grams) of pentane-diol-ZA-bis(tri+ chloroacetate) was-recovered having the following analysis and characteristics:

Appearance, Water :white oily liquid. Example VII .--Hea:ane --diol --2,'5 bisttric'hlor acetate) In a manner after the foregoing example, 8.0 moles -(1200 grams) of trichloroacetic acid together with 3.19 .moles .(460 grams) .oflhexanediol-2,5 and 260 grams of toluene were charged into an esterii-lcation still. The charge was refluxed until no more water was separated which was after 7.77 moles (14.0 grams) of water had been separated. The remaining reaction mixture was vacuum distilled. Three-and-twentyseven-hundredths moles (1338 grams) of hexanediol-2,5-bis(trichloroacetate) was recovered having the following analysis and characteristics:

Appearance, Water white oily liquid.

The foregoing examples illustrate our preferred method for preparing preferred trichloroacetic acid diesters of this invention, from dihydroxy aliphatic alcohols of the type BAOI-Dz wherein R is a radical selected from the group CnH2n and (CnHZn) wherein n is a whole num her from two to six, inclusive, however, it is to be understood that we do not wish to be limited thereto because dihydroxy aliphatic alcohols, higher in the glycol series than those of the foregoing formula wherein n is a whole number from two to six, may be successfully used in accordance with this invention to produce valuable trichloroacetic acid diesters.

The compounds of this invention each contain two trichloromethyl groups. These groups makev the compounds particularly useful; especially the lower members of the series, as given in the foregoing examples; since they are non-flammable and retard combustion when incorporated into resins; e.. g. cellulose resins, such as cellulose acetate and cellulose ethers; in which they also serve the dual purpose of plasticizing such resins. In addition, the novel esters are useful as plasticizers for vinyl resins, e. g. vinyl halides, vinyl esters and vinyl acetals. However, we have determined that the esters of this invention evolve l-ICl at a very slow rate on standing. This characteristic would render them undesirable for use as plasticizers in synthetic resins, except that we have found that the stability of these esters, against decomposition resulting from aging or exposure to heat whereby hydrogen chloride is,

split off, may be vastly improved by incorporating therein a stabilizing amount of an alkene oxide;

For example, by incorporating between about one-half and one per cent of propylene oxide, or preferably a higher boiling alkene oxide stabi; lizer, such as, phenoxy propylene oxide or poly meric epoxides, into the compounds of this invention, there is no detectable evolution of hydrogen chloride from such a stabilized sample,

which has been standing more than three months in a glass bottle stored under normal room conditions; .Moreover, hydrogen chloride.zevolutibn' conditions and insoluble in water, particularly as compared'to the sodium salt of trichloroacctic acid which is .a known herbicide, and :whenapplied .for such purpose will .not evaporate, or'be dissolved and thereby removed by rainfall.

The following examples further illustrate .the use of :the compounds of this invention as plasticizers ior'resins.

Example VJI'I Forty parts of ethylene glycol bis(trichloroacetate) which had been given a preliminary stabilizing treatment by washing with an aqueous solution of sodium bicarbonate, parts of cellulose acetate powder and four-tenths part of phenoxy propylene oxide, a high boiling alkene oxide stabilizer, were mixed and milled on a rolling mill, at a temperature of about degrees centrigrade, for about five minutes. The resulting sheet of resin was about one-sixteenth of an inch thick, and was clear, colorless and pliable; however, it could be pulverized into a molding powder, which powder could, in turn, be pressure molded at a temperature of about 160 degrees centigrade to produce a substantially solid stable colorless resin of any desired moldable shape. A sample of the sheet of resin produced by milling was tested for heat stability by an accelerated aging test which established that cellulose acetate plasticized with stabilized ethylene glycol bis(trichloroacetate) remains unchanged in color when heated one hour at a temperature of 160 degrees centigrade and that on heating for two hours at 160' degrees centigrade, a pale faint yellow color develops.

Example IX oxide stabilizer, were mixed, and milled on a rolling mill, at a temperature of about 160 degrees centigrade, for about five minutes. The resulting sheet of resin was about one-sixteenth of an inch thick, and was clear, colorless, and pliable; however, it could be pulverized into a molding powder, which powder could, in turn, be pressure molded at a temperature of about 160 de-' grees centigrade to produce a substantially solid stable colorless resin of any desired moldable shape. A sample of the sheet of resin produced by milling was tested for heat stability by an accelerated aging test which established that cellulose acetate plasticized with stabilized diethylene glycol bis(trichloroacetate) remains unchanged in color when heated one hour at a temperature of 160 degrees centigrade and that on heating for two hours at 160 degrees centigrade, a pale faint yellow color develops.

The last two preceding examples illustrate the use of the compounds of this invention as plasticizers for synthetic resins; however, we do not intend that our invention shall be limited thereto, as We contemplate still other 'uses for our novel compounds and compositions or formulations thereof, including use as fungicides, insecticides, fumigants, seed sterilization agents plant hormones, and as rubber accelerators.

REFERENCES CITED The following references are of record in the file of this patent:

- UNITED STATES PATENTS Name Date Borglin Feb. 10, 1942 OTHER REFERENCES Whitemore: Organic Chemistry, (Van Nostrand Co., New York, 1951), 2nd edition, p. 523.

Scattergood et al.: J. Am. Chem. 800., vol. '72 pp. 2808-2809 (June 1950).

Karrer: Organic Chemistry 2nd English ed. (Elsevier Publ. Co.; New York; 1946), p. 622.

Number 

2. TRICHLOROACETIC ACID DIESTERS OF DIHYDROXY ALIPHATIC ALCOHOLS SELECTED FROM THE GROUP CONSISTING OF ALKYLENE GLYCOLS AND ALKYLENE GLYCOL ETHERS, WHEREIN THE NUMBER OF CARNON ATOMS CONTAINED IN THE ALKYLENE GROUP IS FROM TWO TO SIX, INCLUSIVE. 